The use of laminates of a conductive species adhered to flexible nonconductive substrates to form etched circuit patterns is gaining widespread use, particularly in the preparation of microwave integrated circuits. However, circuit patterns prepared from such laminates or "circuit board" material currently commercially available often fail to provide circuits of the requisite high degree of resolution for microwave application.
Etched circuit patterns are typically generated by etching away unmasked conductive material with a solution of suitable etchant. In the final stages of the etching process, a portion of the conductive species which has been etched away may redeposit on the exposed substrate surfaces adjacent the circuit pattern. Although redeposition generally occurs to some degree over the entire exposed substrate surface, it is generally deepest at the base of the walls of the etched pattern. Upon plating of the pattern with protecting layers of metals, the plating materials effectively attach not only to the conductive pattern, but also to the redeposited conductive material lying adjacent thereto. The result is a widening of the circuit pattern or "halo" effect which drastically impairs the performance of the circuit pattern, particularly for microwave applications. What is needed is a method of eliminating redeposited conductive species during the etching process to insure that the circuit pattern side walls and adjacent exposed substrate surfaces are essentially free of redeposited conductive material.